Analysis and Recommendations for Your Eye Cream Formula

Thank you for providing your eye cream formula and detailed questions. Based on the ingredients and the issues you've encountered, here is an analysis and recommendations:

1. Cause of the Rancid Smell

The rancid smell you are experiencing after 5 months is indeed likely due to oxidation, specifically of the natural oils in your formula. As the staff mentioned, Rose Hip Oil and Sweet Almond Oil are particularly prone to oxidation because they contain high levels of unsaturated fatty acids. These fatty acids react with oxygen over time, leading to the unpleasant odor characteristic of rancidity. Rose Hip Oil can also have a naturally nutty scent that some might perceive as slightly rancid even when fresh.

2. How to Remedy Rancidity

Preventing rancidity in formulations with sensitive oils requires a multi-faceted approach:

• Antioxidants: Adding antioxidants like Vitamin E (Tocopheryl Acetate) can help, as you suggested. However, as noted by both the staff and C7, while Vitamin E offers some protection, it may not be sufficient on its own for oils highly susceptible to oxidation over a long period. Rosemary Oleoresin Extract (ROE) is another potent antioxidant for oils, but it has a strong scent and color.
• Choose More Stable Oils: The most effective way to prevent rancidity is to use oils that are naturally more stable. C7 recommended oils like Jojoba Oil (both Golden and Clear deodorized types), Squalane (Olive), and Olive CLEAR (Hydrogenated Olive Oil). These oils have a longer shelf life and are less prone to oxidation compared to Rose Hip Oil and Sweet Almond Oil. You could consider replacing or reducing the amount of Rose Hip Oil and Sweet Almond Oil with one or a combination of these more stable options.
• Packaging: Use packaging that protects the product from light and air, such as opaque bottles or airless pumps.
• Storage: Store the finished product in a cool place, away from direct sunlight and heat. Refrigeration (4-8°C) is ideal for extending the life of products containing sensitive oils.

Regarding the slight increase in viscosity, this could potentially be related to changes in the oil phase over time due to oxidation or other interactions within the formula.

3. Formula Effectiveness for Eye Area Concerns

Your formula contains several active ingredients known to address eye area concerns:

• REGU-AGE: This ingredient is specifically designed to reduce dark circles and puffiness by improving microcirculation and strengthening the skin around the eyes. It also helps reduce inflammation and protects against UV damage.
• Argireline (Acetyl Hexapeptide-8): This peptide works by reducing muscle tension, which helps to reduce the appearance of expression wrinkles, particularly around the eyes and forehead.
• Pep-Coll (Palmitoyl tripeptide-5): This peptide stimulates collagen production, which improves skin firmness and reduces the depth, width, and length of wrinkles.

Combined with moisturizing ingredients like Double Hyaluron Liquid, Beta Glucan, Allantoin, Shea Butter Ultra Soft, Rose Hip Oil, and Sweet Almond Oil, your formula has a good foundation for addressing wrinkles and providing hydration and soothing benefits. As the staff suggested, incorporating Caffeine (Coffee Extract) and Safe-B3 (Vitamin B3, Niacinamide) could further enhance the formula's effectiveness for reducing dark circles and puffiness by stimulating blood flow, and Safe-B3 also offers anti-aging and skin-strengthening benefits.

4. Mixing 'full & lift' (Lift-Now™)

'full & lift' is likely referring to Lift-Now™, an ingredient that provides a temporary skin-tightening effect. If it is not properly heated or mixed into the cream base, it may not fully dissolve or disperse. This could lead to an uneven texture or potentially affect the stability of the emulsion over time, although the staff mentioned that if it doesn't integrate, you would typically see separation issues. If you are concerned about proper dispersion, ensure you follow the recommended mixing instructions, which usually involve mixing it into the water phase. If you consistently face issues or prefer a simpler process, you could consider omitting it, especially if the temporary lifting effect is not a primary goal for your eye cream.

5. Antioxidant Efficacy of Other Ingredients at Low Concentrations

Yes, it is correct that some ingredients primarily known for other benefits (like whitening or anti-aging) may also possess antioxidant properties. According to the staff, using these ingredients at the minimum recommended concentration for their antioxidant effect can indeed provide that benefit, even if the impact on whitening or wrinkle reduction is minimal at that low dose. If you have such ingredients in mind, you can check their recommended usage rates for antioxidant activity to see if they can serve a dual purpose in your formula and potentially reduce the need for additional dedicated antioxidants like Vitamin E.

Oil Selection for Different Creams

Based on the discussion with C7 and the product descriptions, here are some considerations for selecting oils for different cream types for normal to dry skin:

• Eye Cream: Given the sensitivity of the eye area and the desire to avoid rancidity, stable oils are highly recommended. Jojoba Oil (Golden or Clear deodorized), Squalane (Olive), and Olive CLEAR (Hydrogenated Olive Oil) are excellent choices due to their stability and skin compatibility. They provide moisture and a pleasant feel without being overly heavy.
• Day Cream: For a day cream, you might prefer lighter oils that absorb well and don't leave a greasy feel, especially if applying makeup afterward. Stable oils like Jojoba Oil and Squalane (Olive) are suitable. Safflower Seed Oil is also an option, though C7 suggested testing it first for stability. Olive CLEAR could also work for a non-greasy feel.
• Night Cream: Night creams can often be richer to provide intensive hydration and nourishment overnight. You could use a combination of stable oils and potentially include a small amount of a richer butter. Shea Butter (both Ultra Soft and Refined/Deodorised) is a good option for richness and moisturizing properties. Cocoa Butter Replacer or Coconut Butter could also contribute to a heavier feel, but consider their texture and melting points. Stable oils like Jojoba Oil, Squalane (Olive), and Olive CLEAR can still form the base.

Regarding the different types of Shea Butter and Cocoa Butter:

• Shea Butter (Refined, Deodorised) vs. Shea Butter (Ultra Soft): The Refined/Deodorised version is processed to remove scent and color and is a harder butter at room temperature. The Ultra Soft version is specially processed to maintain a consistent soft texture without oil separation. For a thicker, heavier cream, the Refined/Deodorised Shea Butter might contribute more to the solid structure, while the Ultra Soft provides a smooth feel. Both offer moisturizing benefits.
• Cocoa Butter vs. Shea Butter: Cocoa Butter (or its replacer) tends to be harder and has a distinct chocolate-like scent in its unrefined form (though replacers are deodorized). It provides richness and a protective barrier. Shea Butter is generally softer and known for its excellent moisturizing and skin-healing properties. The choice depends on the desired texture, feel, and any scent preference (if using unrefined versions). Cocoa Butter Replacer is designed to mimic the properties of Cocoa Butter but with improved stability and no scent/color issues.

In summary, to address the rancidity issue, prioritize using more stable oils and ensure proper packaging and storage. Your current formula has good anti-aging ingredients, and adding Caffeine and Safe-B3 could enhance its effectiveness for dark circles and puffiness. Pay attention to the mixing of ingredients like Lift-Now™ for optimal texture. Consider the properties of different oils and butters when formulating your day and night creams for normal to dry skin.